The present invention is directed to a method and apparatus for forming sub-micrometer structures on a substrate. In one embodiment, these structures can be magnetic poles of thin film heads for data storage devices.
Many electronic products require the construction of miniature metallic structures. An example of such a structure is the second pole tip of a thin film recording head. Conventional processes for the fabrication of magnetic recording heads often comprise a combination of lithographic, deposition, plating, and etching processes. Typical recording heads are formed on Al2O3/TiC ceramic wafers that are eventually formed into sliders that fly over magnetic disks to perform read and write functions.
In a thin film recording head, it is desirable that the width of the pole tip of a second pole piece is made as narrow as possible in order to increase track density, which represents the number of tracks per inch width of the recording medium on which the head writes. The higher the track density, a greater number of bits per a greater area can be stored on the magnetic medium. The effort to produce narrower trackwidths is a constant challenge to the field.
One conventional method of creating pole structures is to fabricate a mask or xe2x80x9cresist frame for platingxe2x80x9d in conjunction with an electroplating process. For example, a conventional image transfer process to create an anisotropic cavity or trench in a semiconductor device, with the cavity having a seedlayer as the floor, is discussed in U.S. Pat. No. 5,665,251 (the ""251 patent) and is shown in FIG. 1.
In FIG. 1, a seedlayer 11 is formed over a substrate 10. A thick photoresist layer 12 is formed over seedlayer 11. A masking layer 13 is formed on top of the thick photoresist layer 12, then a thin photoresist layer 14 is formed on masking layer 13.
The magnetic pole structure then can be created on the seedlayer 11 in the cavity 16, with the seedlayer providing an electrical path to the structure. A portion 15 of thin resist layer 14 is first removed in steps 101 (exposure to light) and 103 (wet development with an aqueous solution). In step 105, mask layer 13 is etched by a reactive ion etching (xe2x80x9cRIExe2x80x9d) process. To create the cavity, thick layer 12, typically of polymeric photoresist, is etched (in step 107) using a RIE process. RIE is used to etch the thick layer because RIE can produce highly anisotropic cavities. However, RIE can also damage the underlying seedlayer. To prevent this damage during photoresist etching, a deposition of a protective layer, such as alumina or silicon dioxide, (not shown), can be formed on top of the seedlayer 11. After the creation of the cavity, the protective layer in the bottom of the cavity is removed in a subsequent step which does not damage the seedlayer nor undercut the thick layer. An electro-deposition process (step 109) is used to form a pole structure 18. The remaining thick photoresist layer 12 is then removed by further RIE etching.
It is desirable, however, to improve upon conventional processes, such as the process described above, in order to fabricate narrower pole structures for greater track densities on recording media. Such narrower pole structures preferably would have widths less than about 0.3 micrometers (xcexcm).
In view of the foregoing, it would be desirable to provide a process for the fabrication of sub-micrometer structures on a substrate. According to one embodiment of the present invention, a method for fabricating a multi-layer electroplating mask for the formation of a submicrometer structure is provided. The multi-layer electroplating mask includes a substrate, a seedlayer deposited on the substrate, a first photoresist layer deposited on the seedlayer, a hard mask layer deposited on the first photoresist layer, and a second photoresist layer (or image layer) deposited on the hard mask layer. The first photoresist layer preferably is thicker than said second photoresist layer. The method includes performing a photoresist etch of the first photoresist layer to define a trench having vertical sidewalls. After the photoresist etch, a silylation of the trench is performed for a predetermined period of time to narrow the trench in width. From this electroplating mask, structures, such as magnetic pole pieces, can be formed having widths of less than or equal to 0.3 micrometers. Of course, the present invention can be used to form structures having widths greater than 0.3 micrometers if desired.
According to another embodiment of the present invention, a method for fabricating a multi-layer electroplating mask for the formation of a submicrometer structure is provided. The multi-layer electroplating mask includes a substrate, a seedlayer deposited on the substrate, and a photoresist layer deposited on the seedlayer. The photoresist layer has a thickness of about 4 micrometers to about 6 micrometers. The method comprises lithographically patterning the photoresist layer with an exposure to light to define a trench having vertical sidewalls. A silylation of the trench is performed for a predetermined period of time to narrow the trench in width. From this electroplating mask, structures, such as magnetic pole pieces, can be formed having widths of less than 0.3 micrometers.
Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.